introduce --oom-score-adj

enter.c

@@ -71,6 +71,29 @@ static void apply_rlimit(int resource, struct rlimit const *value)
 	}
 }
 
+ssize_t write_oom_score_adj(long value)
+{
+	int fd = open("/proc/self/oom_score_adj", O_WRONLY);
+	if (fd == -1) {
+		return -1;
+	}
+
+	char data[BUFSIZ];
+	if ((size_t) snprintf(data, sizeof (data), "%ld\n", value) >= sizeof (data)) {
+		errx(1, "'%ld\n' takes more than %zu bytes.", value, sizeof (data));
+	}
+
+	ssize_t written = write(fd, data, sizeof(data));
+	if (written == -1) {
+		return -1;
+	}
+
+	if (close(fd) == -1) {
+		return -1;
+	}
+	return written;
+}
+
 static int sig_handler(int epollfd, const struct epoll_event *ev, int fd, pid_t pid)
 {
 	siginfo_t info;
@@ -315,6 +338,10 @@ int enter(struct entry_settings *opts)
 		err(1, "close timens_offsets");
 	}
 
+	if (write_oom_score_adj(opts->oom_score_adj) == -1) {
+		err(1, "writing oom_score_adj");
+	}
+
 	/* Setup a socket pair for file-descriptor passing. Used by pty allocation. */
 	enum {
 		SOCKET_PARENT,

enter.h

@@ -93,6 +93,8 @@ struct entry_settings {
 	struct climit climits[MAX_CGROUPS];
 	size_t nactiveclimits;
 
+	long oom_score_adj;
+
 	const char *arch;
 
 	struct bst_rlimit rlimits[BST_NLIMIT];

main.c

@@ -56,6 +56,7 @@ enum {
 	OPTION_CLIMIT,
 	OPTION_CLIMIT_TRY,
 	OPTION_PIDFILE,
+	OPTION_OOM_SCORE_ADJ,
 	OPTION_IP,
 	OPTION_ROUTE,
 	OPTION_NO_FAKE_DEVTMPFS,
@@ -304,6 +305,7 @@ int main(int argc, char *argv[], char *envp[])
 		{ "cgroup",             required_argument, NULL, OPTION_CGROUP          },
 		{ "limit",              required_argument, NULL, OPTION_CLIMIT          },
 		{ "try-limit",          required_argument, NULL, OPTION_CLIMIT_TRY      },
+		{ "oom-score-adj",      required_argument, NULL, OPTION_OOM_SCORE_ADJ   },
 		{ "pidfile",            required_argument, NULL, OPTION_PIDFILE         },
 		{ "ip",                 required_argument, NULL, OPTION_IP              },
 		{ "route",              required_argument, NULL, OPTION_ROUTE           },
@@ -424,6 +426,13 @@ int main(int argc, char *argv[], char *envp[])
 				handle_climit_arg(&opts, optarg, false);
 				break;
 
+			case OPTION_OOM_SCORE_ADJ:
+				opts.oom_score_adj = strtol(optarg, NULL, 10);
+				if (errno != 0) {
+					errx(1, "oom score adjustment must be an integer");
+				}
+				break;
+
 			case OPTION_SHARE:
 				process_share(opts.shares, optarg);
 				break;

outer.c

@@ -440,6 +440,7 @@ void outer_helper_spawn(struct outer_helper *helper)
 	}
 
 unshare:
+
 	if (helper->unshare_user) {
 		burn_uidmap_gidmap(child_pid, helper->uid_desired, helper->gid_desired);
 	}

usage.txt

@@ -52,6 +52,7 @@ Options:
       --rlimit <res>=<hard>:<soft>,
       --rlimit <res>=<value>        Set the specified resource to the provided
                                     value(s).
+      --oom-score-adj <value>       Adjust the OOM score for the process.
       --pidfile <path>              Write PID in file and exclusive-lock it.
       --tty[=<options>]             Allocate a pty for the process.
       --close-fd[=<fd>|<from>-[to]] Close specified file descriptor or fd range